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Signal from tissue will always be present within the lumen of vessels or in the heart. To image blood flow, this clutter needs to be suppressed sufficiently for the weaker blood signal to appear. As the magnitude and direction both of surrounding tissue and blood flow varies throughout the cardiac cycle, non-adaptive clutter filters will inevitably either yield dropouts or a significant tissue velocity...
Keloid is a kind of benign dermal lesion that caused by the collagen deposition and growth beyond the boundaries of the original wound margin. Many studies have reported that the density of blood vessel within keloid is higher than normal skin. Therefore, the density of blood vessel is the potential determinant for understanding the pathogenesis of keloids. However, to date, the techniques for extracting...
The beamformer plays a crucial role in increasing the quality of images acquired with an ultrasound imaging system. Numerous beamforming methods have been introduced, evaluated and reported with substantial improvement in resolution and contrast, compared with conventional delay-and-sum (DAS) beamforming. Better beamforming should not only provide high quality images, but the image should also be...
In medical ultrasound B-mode imaging, by increasing the image contrast, spatial and temporal resolution, it will help to improve the diagnostic and decision making process. Previously the unsharp masking (UM) techniques have been successfully implemented for digital image processing as edge enhancement techniques. However, the outcomes of the method are limited and influenced by the image formats...
Singular value decomposition (SVD)-based clutter filtering has demonstrated superior clutter rejection performance in the emerging field of ultrasound microvessel imaging. To alleviate the computational burden of SVD, here we present a fast and robust clutter filter using randomized SVD (rSVD) and randomized spatial downsampling (rSD). rSVD accelerates SVD by approximating and removing the first k-order...
Self-localization is one of the most critical parts in robotics and automated driving. Thus, it is quite essential to have some kind of self-assessment for the respective pose estimate. Therefore, this paper introduces a new online approach to check the consistency of feature-based random-set Monte-Carlo Localization (MCL). The basic idea is to detect inconsistencies of the assumed measurement process...
Echocardiographic image sequences are frequently corrupted by quasi-static artifacts known as “clutter”. These artifacts are superimposed on the moving myocardium and hinder useful diagnosis. Prior work has shown the efficacy of blind source separation methods to suppress clutter while retaining underlying signal. However, the same image may be corrupted with clutter from multiple mechanisms or sources...
Code fragments posted in answers on Q&A forums can form an important source of developer knowledge. However, effective reuse of code fragments found online often requires information other than the code fragment alone. We report on the results of a survey-based study to investigate to what extent developers perceive Stack Overflow code fragments to be self-explanatory. As part of the study, we...
Epi-optoacoustic (OA) imaging allows flexible clinical use, but out-of-plane and echo clutter from strong OA sources limits contrast. In localized vibration tagging (LOVIT), a focused ultrasonic pushing beam creates transient localized displacement and thus a signal phase shift. Subtraction of OA acquisitions before and at the peak displacement highlights signal from the focus and eliminates out-of-plane...
Doppler measurements in coronary arteries are difficult due to rapid motion of the myocardium and small vessel dimensions. High frame rate 3D Doppler imaging with retrospective spectral Doppler processing could potentially solve this. However, the combination of low blood flow velocities and excessive tissue motion in parts of the cardiac cycle makes clutter suppression challenging. In the present...
Recently, ultrafast ultrasound imaging has been proposed for many clinical applications. However, most operational frequencies of ultrafast ultrasound imaging are around 3.5 to 15 MHz. Currently, ultrafast 40 MHz high frequency ultrasound imaging has been developed in our Lab. High frequency ultrasound is a good choice for blood flow mapping because the backscattering signals from blood is increased...
Nonlinear shear waves have a cubic nonlinearity which generates a unique odd harmonic signature. This behavior was first observed in a homogeneous gelatin phantom with ultrafast plane wave compounding ultrasound imaging and correlation-based tracking algorithm that determines particle motion. However, in heterogeneous tissue, like brain, clutter degrades motion tracking and destroys the weak odd harmonics...
Carpal tunnel syndrome (CTS) is the most common wrist neuropathy. Ultrasound can image the tendons in real-time, enabling analysis of tendon dynamics. We earlier developed and validated a speckle tracking algorithm [1] using Normalized Cross Correlation (NCC) on a stationary region of interest (ROI) over the tendon path (Fig 1a). However, NCC is sensitive to clutter and shadows which lead to motion...
Over the past years, the design principle for clutter removal has remained basically the same. The clutter signal has been separated from the blood signal based on the difference in their spectral frequencies. This design presents a major challenge for angle independent estimators, because at high beam-to-flow angles tissue and blood frequency spectra tend to overlap. This work presents a novel filtering...
Ultrasonic perfusion imaging requires high sensitivity to slow disorganized blood-flow patterns while simultaneously rejecting clutter and noise. We achieve high sensitivity to both vascular flow and perfusion without contrast enhancement by adopting the following sampling pattern. Doppler pulses sampled at 1 kHz were acquired to form a Doppler frame. Frames were recorded at 10 Hz over 10 seconds...
A multi-frame rate plane wave imaging strategy is developed to simultaneously image tumor vasculature and quantify tumor perfusion. Customised imaging sequences interleaving a short but high frame rate (HFR) plane wave imaging sequence with a long but low frame rate imaging (LFR) sequence were implemented using a programmable ultrasound research platform. The results from a spatio-temporal coherence...
The elastic properties of human tissue can be evaluated through the study of mechanical wave propagation using highframe rate imaging and motion estimation. Methods such as block-matching or phase-based motion estimation are usually used to estimate the motion induced by the mechanical wave. These methods can be time consuming because of the processing involved and the need for specific types of averaging...
Linearly polarized nonlinear shear waves have a cubic nonlinearity which generates shear shock waves. This behavior has been only observed in a homogeneous gelatin phantom with ultrafast plane wave ultrasound imaging and a correlation-based tracking algorithm to determine particle motion. However, in heterogeneous soft tissue, such as brain, clutter degrades motion tracking. We propose a high frame-rate...
We trained deep neural networks (DNNs) to suppress off-axis scattering. The networks operated on sub-band ultrasound channel data in the frequency domain and a different network was trained for each frequency. The in-phase and quadrature components of the signals were treated as separate inputs to the network and the output structure was the same as the input. An inverse short-time Fourier transform...
Recent studies have shown the ability of concurrent spatial-temporal processing methods such as singular value decomposition (SVD) filtering in visualization of the small vessels without using any type of contrast agents. The vessel images resulting from SVD filtering suffer from local and global residual background that limit the visibility of the entire vessel networks within a fixed dynamic range...
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